This paper investigates the extent of second language (L2) use in domains belonging to inner speech. The participants consist of 149 highly educated L2-competent sequential Polish-English bilinguals resident in the UK*. The independent variables include acculturation level, social network profile, length of residence, and predicted future domicile. The study combines both quantitative and qualitative approaches. All participants completed an online questionnaire, and 14 of these were also interviewed by the researcher. Results show that bilinguals who acculturate to a higher level, operate in majority L2-speaking social networks, and intend to remain in the UK indefinitely, use significantly more L2 across domains belonging to inner speech.